The invention relates to a motor vehicle steering system, an assembly tool and an assembly method for a motor vehicle steering system.
The hitherto existing direct screwing of the steering spindle members with one another in the engine compartment is only possible in the combined field of exhaust gas systems, catalytic converters, engines and transmission lines with considerable effort. Here, one spindle member is screwed together with the other spindle member, which is also referred to as a steering coupling if it is arranged at the end of the steering spindle rod, transversely with respect to the steering spindle direction. In the case of vehicles having front engines, this results in very poor accessibility of the components to be connected and the number of variants of arrangements for optimizing the accessibility for different engine variants and steering systems, such as left and right-hand drive models, increases significantly. In addition, standard assembly sequences, such as the time of assembly of the exhaust system, are hardly complied with or are not complied with at all.
DE 10 2008 006 497 A1 describes an assembly arrangement for connecting an upper steering spindle member to the steering coupling. The end of the steering spindle member is introduced into an end-side receiving region of the steering coupling, wherein the assembly arrangement comprises a device to ensure that the steering spindle member and the steering coupling can be aligned coaxially. To that end, the steering spindle member has an end-side hook element, into which a strap loop protruding from the end-side receiving region of the steering coupling is mounted before the final assembly of the engine with the vehicle body. Due to the tight installation space conditions, the steering spindle rod normally impedes the assembly of the engine module with the vehicle body, whereby assembly becomes time consuming and likely to involve injury.
A steering arrangement is known from DE 10 2011 109 691 A1 in which an upper steering spindle member is plugged together with the steering coupling via an intermediate piece arranged on the steering coupling by means of a tongue-and-groove connection aligned axially, wherein a compression spring, which is operatively connected to the intermediate piece, braces the intermediate piece and therefore the steering coupling with the end of the upper steering spindle member. The steering spindle member end is thereby moved axially into the intermediate piece, which is then shifted towards the steering spindle member end against the compression spring force and is hooked onto an undercut of the steering spindle member end formed of an annular groove. The assembly of the steering spindle members, so the steering coupling and upper steering spindle member, with each other does not require any screwdrivers and can be executed without excessive force. The correct relative position of the two steering spindle members is recognized by the installer by means of one or more visual markers, such that incorrect positioning is excluded during assembly. However, in the case of particularly tight installation spaces, the visual marking is difficult to see, which is why assembly is more difficult in these cases.
Based on this prior art, the object arises to create a motor vehicle steering system in which two steering spindle members, in particular an engine compartment side spindle member and the subsequent steering coupling, are able to be connected to each other with minimal effort even in the event of visual inaccessibility.
This object is solved by a motor vehicle steering system.
Furthermore, the object arises to create an assembly tool for a motor vehicle steering system which makes it possible to assemble a motor vehicle steering system according to the invention in a convenient manner, with minimal effort and with a low risk of injury.
This object is solved by an assembly tool for a motor vehicle steering system.
Finally, the object also arises to provide an improved assembly method for motor vehicle steering systems with respect to the quality and speed of the design.
This object is solved by an assembly method for a motor vehicle steering system.
A first embodiment relates to a motor vehicle steering system which has a steering column having a steering spindle, which contains several steering spindle members connected to one another in a non-rotational manner. The steering spindle end of the one steering spindle member has a spline shaft profile positioned in the axial direction on the outer periphery and is thereby introduced into a sleeve-like intermediate piece which is arranged on the other steering spindle member adjacent to the steering spindle in the longitudinal direction, in particular the steering coupling. On the inner periphery, the intermediate piece has a negative-shaped spline shaft profile with respect to the spline shaft profile of the spindle member. The one spindle member is plug-connected to the intermediate piece and therefore to the other spindle member by engagement of the two spline shaft profiles. In other words, the other steering spindle member supports the intermediate piece. A circumferential guide contour pointing towards the intermediate piece is formed on the spindle member, the guide contour being upstream of the spline shaft profile towards the intermediate piece and being perforated by the grooves of the spline shaft profile to form convex guide segments.
The guide contour can be an integral component of the spindle member opposite the intermediate piece, or it can be a separate member joined to this spindle member, According to the invention, the guide contour is arranged in an edge region of the front surface of the end of the spindle member, wherein the guide contour can be an annulus in a top view of this front surface. During processing of the shell surface of the spindle member end or the guide contour, the guide contour is delimited on the end side by a gently multi-curved or undulated design curve path which has at least one low point (i.e. a bulge) and one high point (i.e. an indentation). The bulges or indentations themselves can be symmetrical such that, in the inserted position, the longitudinal axes of the teeth of the spline shaft profile of the intermediate piece run through the “virtual” vertices (indentations) and the longitudinal axes of the grooves run through the actually present vertices (bulges) of the guide contour of the spindle member. In the case of indentations, the vertices are not actually present (i.e. are only to be understood in the sense of a constructive auxiliary point), since they are located in the region of the groove(s) of the spline shaft profile of the spindle member.
The guide contour should therefore help, when bringing the spindle member into contact with the intermediate piece, to make it easier to find the exact and single correct angular position in which the two spline shaft profiles are able to be brought into engagement. The curvatures of the guide contour are thereby formed in such a way that they are not able to interlock with opposite teeth of the spline shaft profile of the intermediate piece but rather slide gently on the upper sides of the teeth of the spline shall profile of the intermediate piece in the event of relative rotation of the two members. The support on the guide contour is transferred from tooth to tooth until the correct angular position is achieved for engagement. This sliding process of the guide contour on the upper sides (or partially on the flanks) of the teeth is to be compared to the sliding of a probe pin on a cam disc, wherein the guide contour performs an oscillating axial movement by means of the characteristic curvatures during rotation of the spindle member about its longitudinal axis or during rotation of the intermediate piece about its longitudinal axis. The guide contour is designed according to the invention in such a way that the axial distance of the one spindle member from the intermediate piece of the other spindle member (steering coupling) is minimal in the engaging position, which an installer, on the other hand, is also able to detect in a tactile manner. The spindle member can be shifted in the axial direction in order to have more freedom of movement during assembly, and can additionally be locked, even in the final assembled position, for example braced.
The embodiment of the end of the steering spindle member according to the invention makes it significantly easier for the installer to introduce this into the intermediate piece of the steering coupling, since the steering coupling is usually arranged in a jagged region in the engine compartment, which is hard to reach by hand (also visually very poorly accessible), of a motor vehicle and it was previously very difficult to determine the correct relative position of the one steering spindle member for steering spindle coupling purely by feeling. With the present invention, an installer can bring together the end of the steering spindle member and the intermediate piece without notchy jamming and therefore detect in a tactile manner whether it is located in the predetermined assembly position.
In a further embodiment, the spline shaft profile can be asymmetrical, wherein the tooth spacings, the tooth widths and/or the tooth depths of the spline shaft profile can be different. The guide contour or the guide segments can furthermore have an undercut opened with respect to the intermediate piece.
By means of such an asymmetrically formed spline Shaft profile, the one spindle member is only able to be introduced into the intermediate piece of the steering coupling at precisely one predetermined angular position, thereby enabling the angular position of the steering coupling to correspond exactly to a predetermined steering wheel position. According to a poka-yoke principle, assembly is simplified through this and sources of error are eliminated. As a result, reworking, which comprises a straight-line positioning of the steering wheel, can be dispensed with. Furthermore, individual tooth/grooves pairs of the spline shaft profile are formed to be tapered on the end side in order to achieve an effective centering of the spindle member assigned to the steering column during insertion into the intermediate piece.
In a further embodiment, the spindle member assigned to the steering column can be hollow at least on its steering spindle end, wherein the intermediate piece has s at least one tongue-shaped protrusion protruding radially inwards on a front side facing the spindle member end, the protrusion engaging with the spline shaft profile of the spindle member assigned to the steering column and preferably being positioned, in particular curved, upwards by a predetermined amount.
“Upwards” here means the direction which points towards the end of the spindle member assigned to the steering column. The respective tongue-shaped protrusion should further facilitate assembly by this being brought into contact or engagement with the guide contour before the spline shaft profile of the steering spindle member end engages with the spline shaft profile of the intermediate piece. This means that the process of aligning the angular positions of the spindle member and steering coupling can already start when both members still have a predetermined axial distance from one another.
The poka-yoke principle can also be fulfilled in the case of a symmetrical spline shaft profile by an additional axially running groove being formed both on the outer side of an individual specific tooth of the spline shaft profile of the spindle member assigned to the steering column as well as in alignment in the adjoining guide segment. This additional groove has its functional equivalent in an additional tooth, which is formed to be negative-shaped, of the spline shaft profile of the intermediate piece. Furthermore, to guarantee the principle, a tongue-shaped special protrusion must be formed on the intermediate piece, the width of which is smaller than the groove width of the additional groove. As such, only individual relative positioning of the spindle members with respect to one another can lead to engagement of the spline shaft profiles with one another, whereby an absolutely clear, correct mounting position is achieved.
The production of the tongue-shaped protrusion is particularly easy to implement when the intermediate piece comprises, for example, a deep-drawn and stamped metal sheet part, wherein the tongue-shaped protrusion can be easily curved out facing upwards. Of course, it is also possible that the spindle member assigned to the steering column is an entirely hollow shaft, for example a telescopic hollow shaft. It is also expedient if one tongue-shaped protrusion is present per tooth of the spline shaft profile of the intermediate piece, wherein these protrusions preferably follow the design of the spline shaft profile in spacing, depth and width. In combination with an at least partial undercut of the guide segments on the front surface facing the intermediate piece, ideal guiding and centering of the guide segments and therefore the spindle member assigned to the steering column results upon insertion with the tongues which are bent out. Due to the undercut, line contact only exists between its one end and the tongues of the intermediate piece.
Alternatively or additionally, an insertion extension can extend coaxially at least from the guide contour of the spindle member in a direction facing the intermediate piece, the insertion extension being introduced into the intermediate piece during plugging together of the two spindle members.
The insertion extension is therefore arranged on the end of the spindle member, seen in the direction of the intermediate piece, substantially in front of the guide contour. This serves to ensure that, during assembly, even before the tongue-shaped protrusions are in contact or in engagement with the guide contour, the spindle member assigned to the steering column is aligned roughly radially on the intermediate piece such that an installer is able to carry out assembly quickly and safely even in the hardly visible, relatively poorly accessible environment. The insertion extension can furthermore have a chamfer on its free end, which further enables insertion. The diameter of the insertion extension can be selected, depending on the performance level to be achieved, at a predetermined amount which is smaller than the internal diameter of the toothing of the intermediate piece spline shaft profile.
According to an alternative embodiment, at least the guide contour and/or the insertion extension can be a part of a plastic plug which is connected releasably to the spindle member.
In this embodiment, the guide contour and/or the insertion extension are not an integral part of the spindle member, but rather a part of a separate member which is connected to the spindle member. Here, plastic is particularly advantageous since it has a low friction coefficient on metals and also does not leave behind surface damage in the form of scratches in the event of unlubricated sliding. In addition, it is also conceivable that the guide contour and/or the insertion extension are injected or vulcanized as a type of collar sleeve onto the spindle member end.
Furthermore, the plastic plug can have a connection extension extending in the axial direction towards the spindle member, the connection extension being plugged into the end of the hollow spindle member, wherein the connection extension preferably supports a circumferential seal, particularly preferably a profile seal, an O-ring or a sealing lip.
The connection extension is thereby plugged into the hollow end of the steering spindle member and primarily serves for the secure fastening of the plastic plug, provided that this is not injected. Furthermore, such a connection extension can help to improve the sealing of the spindle member, from which an improved corrosion resistance results for the spindle member. Surprisingly, however, by using the connection extension, a clear reduction in the sound level in the interior of the motor vehicle can be achieved, since the connection extension acoustically seals the usually hollow spindle member to the greatest extent possible.
The connection extension can furthermore be hollow and the interior of the connection extension can preferably have an expanding means, particularly preferably an expanding rivet.
The expanding means serves for the fastening of the connection extension in the hollow end of the spindle member. The plastic plug having the connection extension is thereby introduced into the hollow end for assembly and the expanding means is then triggered. Alternatively, the connection extension can also be pressed in a classic manner, for which, however, a suitable pressing device is potentially required
A further alternative embodiment refers to the fact that the insertion extension is hollow and at least one engaging means is present on an inner shell surface, preferably a circumferential engaging rib, which is formed to be brought into engagement with an assembly tool.
Here, hollow should also mean that the end of the insertion extension facing the intermediate piece is open. The engaging ribs should thereby optimize the power transmission from the assembly tool to the plastic plug and prevent slipping of the assembly tool. During assembly, the assembly tool can be jammed, hooked or braced in the insertion extension, depending on what appears to be useful. In order to further increase assembly safety, three or more engaging ribs can also be present in the insertion extension.
An assembly tool according to the invention for a motor vehicle steering system has an engaging section, which is able to be brought into engagement with corresponding engaging means of the insertion extension, and a handle connected thereto by means of a connection means.
The connection means can therefore be a flexible section of a string, a wire, a cable or any other elastic core. However, the connection means can also have a predetermined minimum stiffness and shape, such that, during assembly of a motor vehicle steering system from a motor vehicle bottom side, other units present in the engine compartment are able to be guided around. The engaging means can be any engaging means known to the person skilled in the art, such as lugs, adhesive surfaces or a clamping bellows, which is also able to be pressurized.
The assembly method for a motor vehicle steering system according to the invention using an assembly tool according to the invention comprises the following steps:                Preparing and defined positioning of two steering spindle members with respect to each other, preferably a spindle member assigned to the steering column and the steering coupling,        Connecting the engaging section of the assembly tool to the engaging means of the insertion extension of the spindle member assigned to the steering column,        Moving the assembly tool in a direction facing towards the other spindle member (steering coupling),        Separating the assembly tool from the engaging means of the insertion extension of the spindle member assigned to the steering column at a predetermined distance from the steering coupling,        Relative rotation of the steering spindle member assigned to the steering column and of the intermediate piece, until the spline shaft profiles are ready for engagement,        Inserting the steering spindle member end into the intermediate piece to a predetermined end position.        
Since the spindle member assigned to the steering column is usually assembled in the collapsed condition in a motor vehicle shell as a part of an extendible steering column, the use of the assembly tool according to the invention is associated with a greatly reduced workload. The tool is coupled to the steering spindle member end for power transmission and then guided in the direction of the steering coupling, wherein the steering spindle member is shifted, for example, in the sliding seat. If the steering spindle member end is reached at the predetermined (relatively small) distance from the steering coupling, then the assembly tool can be disconnected and the installer can connect the spindle member to the intermediate piece without having to strain, so is ergonomically advantageous, as is described above.
These and other advantages are demonstrated by the description below with reference to the accompanying figures. The reference to the figures in the description serves for the simplified understanding of the subject matter. Subject matters or parts of subject matters that are essentially the same or similar can have the same reference numerals added to them. The figures are only a schematic depiction of one embodiment of the invention.